Lydia Wegman/RTP/USEPA/US 

11/16/2007 03:45 PM

	

To

hking@omb.eop.gov, rjohannson@omb.eop.gov, mschwab@omb.eop.gov

cc

murphy.deirdre@epa.gov, martin.karen@epa.gov, Kevin
Cavender/RTP/USEPA/US@EPA, Mark Schmidt/RTP/USEPA/US@EPA,
Orlin.David@epamail.epa.gov, wallace.larry@epa.gov, Tricia
Crabtree/RTP/USEPA/US@EPA, wegman.lydia@epa.gov

Subject

Responses to your Pb questions  









Heidi,

Attached are our responses to the lead questions you raised last week. 
The responses are provided under each individual question.   Let us know
if you have more questions.   Thanks. 

 ----- Original Message -----

  From: "King, Heidi R." [Heidi_R._King@omb.eop.gov]

  Sent: 11/09/2007 05:53 PM

  To: Lydia Wegman

  Cc: "Johansson, Robert" <Robert_C._Johansson@omb.eop.gov>; "Schwab,
Margo" <Margo_Schwab@omb.eop.gov>

  Subject: Pb NAAQS follow up questions to 11/8 mtg

Lydia,

 

Our thanks to your team for the Pb NAAQS review on 11/8.  We have a few
follow up questions:

 

1)     Slide 12 shows Pb emissions tpy/1000 m2.  To get a better sense
for current levels, what do we think this map would look like if
displaying µg/m3 using Max Qtr?  Also, µg/m3 using Max Monthly?

Response:  Slide 12 is presenting Pb emissions (tpy/1000 m2) from
stationary sources in the 2002 NEI.  Air concentrations (based on
2003-05 monitoring data) in terms of µg/m3 using Max Qtr and Max
Monthly are shown on slides 15 and 16, respectively.  [These are from
Figures 2-11 and 2-12 in the Staff Paper.]  The emissions information in
the NEI is not available in terms of max quarterly or max monthly
estimates.

 

2)     We would like to learn more about Policy Relevant Exposures. 
Please send us the scientific studies that specifically link inhalation
of pb in the ambient air to blood pb, controlling for the influence of
the other ways in which ambient pb would influence blood pb. In your
presentation you said that post 1978 studies how that the ‘air to
pb’ ration is between 1-3 and 1-10.  We are interested in how one can
empirically document the ‘inhalation’ component separate from the
secondary pathway (deposition on surfaces, thus contact through
ingestion of food and hand mouth contact).

Response:  The ratios mentioned in the briefing (and recognized on pages
91-92, 115) pertain to all pathways of exposure to ambient air Pb and
are not limited to the inhalation pathway.  These are discussed in the
1986 CD, p. 1-101 and Section 11.4.1.9 and in a review article by
Brunekreef (1984. The relationship between air lead and blood lead in
children: a critical review. Science of the total environment, 38:
79-123).  A more recent paper identified in the 2006 CD (pp. 3-23 to
3-24) from which such a ratio can be derived is Hilts (2003. Effect of
smelter emission reductions on children's blood lead levels. Sci Total
Environ. 303: 51-58). 

 

3)     How is lead resuspension controlled across large geographies when
historical deposits are a significant contributor to airborne lead
levels?

Response:  Our current guidance for Pb emissions recommends the use of
PM-10 fugitive dust control measures  to address resuspension issues
related to historical deposits of lead.  The controls that are commonly
recommended are the use of fugitive dust suppressants (such as chemical
or oil based surfactants, or water) and covering the affected surface
with vegetation (such as grass or shrubs) to hold the soil in place to
reduce the possibilities of resuspension. Other control measures include
restricting public access to the affected areas to prevent the soil
crust from being disturbed, and in some cases paving the affected
surfaces.  In other more severe cases (usually Superfund areas), to
prevent resuspension, the recommended approach is to remove the affected
top soil from the area, replacing it with uncontaminated soil,  and
disposing of the affected soil.  

4)     Given the decline in the number of monitoring sites, how is
attainment currently demonstrated?  How would it be demonstrated if a
lower NAAQS were adopted?  Would monitoring be similar or identical for
both quarterly and monthly?

Response: 

	NAAQS compliance is demonstrated based on available monitoring data. 
Areas that do not have monitors would be classified as "Unclassifiable"
if the EPA were to redo Pb designations.  

	The NAAQS would still be demonstrated based on monitoring data if the
NAAQS is lowered.  However, we have noted that the current monitoring
network may not be adequate for identifying areas with the potential to
exceed the NAAQS, especially if the NAAQS is lowered.  As such, we plan
to amend the monitoring requirements for Pb in a way that would lead to
better monitoring coverage in those areas with the potential to exceed
the NAAQS.  This issue is discussed in more detail in Section 5 of the
ANPR.

	Currently, monitoring is required on a 1 in 6 day sampling frequency. 
This would only provide only 5 samples on average per month.  We believe
that 5 samples per month would not lead to a statistically significant
estimate of the average for the month.  As such, we are considering
changing the sampling frequency to a 1 in 3 day schedule.  We are also
considering other options (a sliding frequency based on previous Pb
concentrations) to minimize the monitoring burden where there is little
to potential to exceed the NAAQS.  This issue is discussed in more
detail in Section 5 of the ANPR.

5)     Slide 19 suggests that de-listing has been an option.  What
arguments have been proposed toward delisting, and how has EPA responded
to those arguments?

Response:  Arguments proposed toward delisting include recognition that
ambient air concentrations have been reduced substantially since the
standard was set in 1978 and that the Agency has other programs that now
exist to address public health concerns associated with lead, including
the hazardous air pollutant program now in place as a result of the 1990
Clean Air Act Amendments.  More specifically, in comments offered on the
first draft OAQPS Staff Paper, the Battery Council International has
cited legal arguments to support their view that the Agency has the
authority to delist lead as a criteria document and has additionally
stated that the Agency should delist lead (Docket #
EPA-HQ-OAR-2006-0735-0419(1).1).  Discussion of this issue in the final
Staff Paper, notes that notwithstanding changes in air lead
concentrations and emissions, lead continues to be emitted into the air
from numerous and diverse mobile and stationary sources (CAA Section
108(a)(1) ).  Further, currently available studies provide evidence of
adverse health effects associated with blood lead levels and
environmental exposures well below those previously identified, and
there is no discernible threshold for such effects.  The Staff Paper
concludes that consideration not be given to delisting lead.  Delisting
is briefly discussed on pages 86-88 of the ANPR, and on page 102 of the
notice, the Agency solicits comment on the issue.  

 

 

Best regards; have a good weekend

 

heidi

(202) 395-4551

